Turbochargers may improve the performance of internal combustion engines by delivering a greater mass of air to the combustion process, relative to a naturally aspirated engine, thereby allowing a greater amount of fuel to be burned during each combustion cycle and realizing an associated power increase. A turbine wheel is driven by exhaust gasses from the combustion process, and in turn drives a compressor that compresses ambient air and delivers the compressed charge of air to the engine intake to be mixed with fuel for the combustion process.
The pressure of the compressed charge of air delivered to the engine intake must be controlled to prevent over-pressurizing the engine intake, which may lead to engine damage and/or decreased engine performance. A variety of mechanisms and arrangements are commonly used for controlling the pressure of the intake charge. For example, the engine intake may include a blow-off valve which may release excess pressure from the intake manifold. On the exhaust side of the engine, a wastegate may be employed to allow at least a portion of the exhaust gasses from the engine to bypass the turbine, thereby controlling the rotational speed of the turbine and the attendant compression of the intake charge by the compressor.
A wastegate may typically include a mechanical valve which may be operated based on one or more of the turbine rotational speed, intake pressure, engine performance, intake mass air flow, etc. The mechanical valve of the wastegate may be actuated by a mechanical or an electromechanical actuator. Conveniently, a pressure or a vacuum actuator may be used to control the wastegate. Such valves rely on a vacuum source or pressurized air acting against a diaphragm, e.g., working against a spring, to open and close the wastegate.
The vacuum or pressure supplied to the wastegate actuator may be controlled by a solenoid valve, which may be controlled based on any of the foregoing parameters, to operate the wastegate to control the turbocharger boost pressure. A vacuum solenoid valve may include a vacuum and/or pressure port and a port in communication with the wastegate actuator. Often, the vacuum solenoid valve may be a molded plastic component, e.g., molded from glass reinforced nylon, including valve body having a molded valve seat and a Viton® seal. Over time, the nylon valve seat may erode, diminishing the sealing performance. Erosion may eventually lead to exposure of the glass fiber reinforcing material, which may accelerate erosion and/or generate contaminants, e.g., in the form of eroded nylon or Viton® particles, etc. Additionally, contaminants in the valve body may be driven into the nylon valve seat and/or into the Viton® seal during the operation of the valve, decreasing the sealing performance of the valve, and increasing wear or erosion. These various wear mechanisms may reduce the useful life of the valve.